High Occupancy Vehicle lanes (HOV) and High Occupancy Tolling lanes (HOT) are used in highway systems to relieve congestion and increase the human throughput through the highway system. These are often referred to as “car pool” lanes, since the idea is that drivers will drive together in a single vehicle, thus taking vehicles off the road, yet still allowing people to get to their destinations. HOT lanes area more recent element to highway systems. In HOT lanes, single occupant vehicles are allowed to use the HOV lane if they are willing to pay a toll.
A continuing issue with HOV/HOT lanes is enforcement of the HOV/HOT rules of use for the lanes. Typical violation rates are in the 20% to 40% range, while rates have been reported up to 65% on certain highways at certain commute times. The current enforcement regime is manual enforcement by police officers at the side of the road. Police officer based enforcement results in an enforcement rate below 10%. The enforcement revenue generated from police officer based enforcement is a very small percentage of the total potential revenue.
Prior attempts at automated or semi-automated enforcement generally used an imaging system located at a single location, often from the roadside, showed poor performance due to poor line of sight into vehicles, used very costly specialized imaging hardware, and disregarded issues related to serviceability. For example, an illuminator is often used to illuminate the interior of vehicles to enable the imaging hardware to detect the presence or absence of occupants in the passenger seats. Illuminator serviceability is important since, due to the high volume of traffic, life stress is placed on the illuminator bulb. Further, in some installations the traffic lane must be shut down in order to perform service on the illuminator, such as changing the bulb.